The hypothesis of this study is that KT/V urea or total creatinine clearance, both measures of dialysis delivery, will correlate with patient outcomes in children on maintenance PD. This will be a prospective observational study, following children new to PD for 24 months, with dialysis delivery and outcome measured quarterly. Outcome measures will be regressed against dialysis delivery. It is anticipated that at least 120 patients can be enrolled. In order to correctly measure KT/V urea, TBW will be measured in the subjects entered. It is anticipated that this will allow for the elucidation of a predictable, generalizable relationship between total body water and basic anthropometric data, specifically height and weight, in children on PD. GCRC will be used for macro subjects to measure total body water using H2018. The GCRC Mass Spectrometry laboratory will measure total body water (i.e. analyze samples and calculate total body weight) on all enrollees in all centers. Follow-up from entry is 24 months.